1. Field of the Invention
The invention relates generally to laser alignment systems, and more particularly to construction-machine laser automatic control systems for bulldozers, graders, scrapers, excavators and other fine grading machines. Specifically, the present invention relates to-methods and equipment for using several laser reference planes simultaneously for use by one or several pieces of construction equipment.
2. Description of the Prior Art
Some flatwork contractors measure grades with transits and graduated sticks, then string lines and rake base material by hand to meet grade tolerances. A laser-beacon with a rotating light beam output may transmit a signal to indicate the benchmark for a desired grade. Mast-mounted receivers are connected to each end of a grader blade and use such signal to hydraulically raise or lower the blade to match a pre-set grade. An operator simply operates the grader and angles the blade to direct sub-base material right or left as needed, while the laser controls blade height. The laser can promptly make numerous blade adjustments to produce a surface within close tolerance of the grade. Available laser equipment includes a self-leveling laser-beacon that enables dial-in dual-slope grades for drainage. A control panel is mounted on the grader to assist the operator in monitoring progress. If manual control is desired, switches on the grader's steering levers provide fingertip control of the blade in any one or more of multiple directions.
U.S. Pat. No. 4,053,238 for a Self-Leveling Construction Alignment Laser, issued to Lyndell George, et al., Oct. 11, 1977, discloses a system for projecting and using a light beam as a reference line for construction. The system includes a light beam projection device mounted in a housing. A light path compensator is positioned within the housing and intercepts the beam of light emitted by the light beam projecting device and automatically corrects slight deviations of the light beam from true horizontal. A vertically adjustable leg is attached to the front end of the housing and a horizontally pivotable leg is attached to each side of the housing near the rear end of the housing to enable leveling and centering of the housing in a conduit or positioning and leveling on any surface. An indicator, readable from the rear of the housing, is provided for indicating the grade at which the light beam is projected. Structure is connected between the support legs and housing for rotating the housing in a horizontal plane to provide azimuth adjustment of the light beam projected therefrom.
Machine control through XYZ positioning is in its early stages. On-the-fly real-time-kinematic (OTF-RTK) GPS is useful for rough grading, and robotic total stations can satisfy the special requirements of fine grading. Such technologies provide an early indication of what can be achieved with "stakeless surveying" Prior art approaches are not capable of controlling multiple machines on large projects and that require fine grading.